Surge arresters of the above-mentioned kind are previously known from U.S. Pat. No. 4,656,555 and European Patent publication No. 0 230 103. One drawback in these known designs is that if, for example in case of a fault on a varistor block, an arc is produced inside the arrester with an ensuing increase in pressure, parts of the arrester may spread in an explosive manner which is harmful to the environment. Attempts to solve the problem have been made by means of a cross-wound cage, arranged around the arrester stack, with openings for pressure relief (European Patent Publication No. 0 335 480), but this renders the manufacture more complicated and more expensive.